Design and fabrication of wide-angle TE-TM mode splitter in lithium niobate

A novel wide-angle TE-TM mode splitter in a Z-cut lithium niobate is presented. A straight random polarization nickel-indiffused waveguide and a proton-exchanged waveguide bend with substrate prism on the bend corner were combined to form an asymmetric wide-angle Y-branch. The waveguide bend with substrate prism bends the TM wave to the proton-exchanged waveguide with large angle. Hence, the TE wave is left in the straight NI waveguide. The experimental results show that the splitting ratios are 26 dB for the TE mode and 28 dB for the TM mode even at a splitting angle of 7.